The present invention relates to space transportation and more particularly to a method for providing orbital space transportation of a satellite and return of the satellite.
Several deficiencies stand out within the international infrastructure for space transportation and utilization. No capability currently exists for placing small payloads in orbit in a timely, flexible and cost effective manner, supporting the payloads while on-orbit, and returning them and their data to earth with airplane-like utility. These deficiencies become more apparent as time passes. Small payloads become more capable due to quantum improvements in electronic and sensor technologies. Maturing booster and return vehicle technologies in a variety of areas make cost effective solutions practical.
Existing means for returning payloads from space include the American Space Shuttle, the Russian Soyuz and Buran vehicles, and Chinese return capsules. Both Shuttle and Soyuz are large manned vehicles with high costs per flight due to their size and the rigorous safety precautions associated with manned space flight. These vehicles also fly infrequently, and as a result, the payload writing lists are long and many payloads are never flown. Buran is the size of the Space Shuttle and it is intended for manned flight, but it has only flown once in an unmanned mode. The Chinese return capsules are based on 1960's Russian technology. They impose high acceleration loads on their payloads during entry, they are uncontrollable, and their landing point is unpredictable.
Existing means for placing payloads in orbit include a variety of international launch vehicles with payload capabilities ranging from hundreds to hundreds of thousands of pounds to low earth orbit. With one exception, all of these vehicles are ground launched, which does not allow the independent stipulation on inclination and longitude of the ascending node. As a result, a constellation of 15 or 16 satellites are required to observe a region of the earth's surface during every low earth orbit period. Launch and satellite costs preclude the establishment of such orbital configurations and the timely observation of any particular region on the earth. Launch windows for rendezvous and docking and orbiting platforms are also severely constrained for ground launched boosters. And, the lowest achievable inclination without severe payload penalties is limited by ground launching to greater than or equal to the latitude of the launch site.
The one exception is known as Pegasus. Pegasus is disclosed in U.S. Pat. No. 4,901,949, issued to A. L. Elias, entitled "Rocket-Powered, Air-Deployed, Lift-Assisted Booster Vehicle for Orbital, Supraorbital and Suborbital Flight". It is a multistage air-launched vehicle that can place hundreds of pounds into low earth orbit. Air-launching allows independent selection of launch point and launch azimuth, which in turn provides for the independent specification of orbital inclination and longitude of the ascending node. Such orbits are called tailored orbits, and they allow repeated overflight of regions on the earth's surface. Overflights on as many as four successive orbits are possible. Instead of requiring 15 or 16 satellites to observe a region of the earth's surface during every low earth orbit period, only 4 satellites are required. However, Pegasus is purely a launch vehicle and, as such, is neither capable of supporting a payload while on-orbit, nor is it capable of returning a payload to earth.
Due to high launch costs and inadequate means for returning payloads from space, satellites and their payloads are designed for high reliability, long life and robust communications capabilities. Satellite and payload development and production times and costs are high due to this situation. Down linking data through elaborate satellite and ground communications networks often does not allow the data to reach users in a timely manner. And many potential satellite payloads have never been developed due to a lack of a timely, low deceleration, and cost effective return capability.
These deficiencies limit our utilization of space, and to overcome them, the present invention proposes an apparatus which provides a return from orbit capability with airplane-like utility, which supports payloads while on-orbit, and which is air-launched to allow timely achievement of orbits with specified inclination and longitude of the ascending node. These capabilities are made possible by the first time integration of maturing technologies in a variety of areas. These include the Pegasus air-launched booster; low to moderate temperature composite structures; durable thermal protection systems; reliable, light weight and low power avionics; high energy density batteries and deployable and retractable solar arrays; and low weight and high efficiency storable propellant rocket engines.